Pressure-sensitive adhesive having broad useful temperature range

ABSTRACT

Pressure-sensitive adhesive composition, sheet material coated therewith, and a kit for installing insulation around windows comprising the coated sheet material. The adhesive composition consists essentially of a first component consisting essentially of a tackified, emulsifiable adhesive and a second component consisting essentially of at least one terminally unsaturated vinyl monomer, at least one vinyl-unsaturated, homopolymerizable, emulsifier monomer, and, optionally a small amount of an external emulsifier. The adhesive provides high tack and excellent adhesion at both low temperatures and high temperatures, thus rendering it suitable for outdoor use in areas that encounter extremes of weather.

BACKGROUND OF THE INVENTION

This invention relates to pressure-sensitive adhesives and sheetmaterial, including tapes and the like, coated therewith.

Three properties which are useful in characterizing the nature ofpressure-sensitive adhesives are tack, peel strength, and shearstrength. The first measures the adhesive's ability to adhere quickly,the second its ability to resist removal by peeling back on itself froma surface, and the third its ability to hold in position when shearingforces are exerted. Generally speaking, the first two are directlyrelated to each other but are inversely related to the third, cf., e.g.,Sanderson U.S. Pat. No. 4,077,926, Col. 1, lines 31-36. For example,although a given adhesive may exhibit high tack and high peel strength,the shear strength may be unacceptable for the intended purpose.Conversely, while an adhesive may exhibit high shear strength, the tackand peel adhesion may be unacceptable for the intended purpose. Theseshortcomings are often exacerbated at extremes of high and lowtemperature.

Modern industry presents a number of situations where pressure-sensitiveadhesive products having balanced properties (i.e., excellent tack, peelstrength, and shear strength) would be highly desirable. Some examplesof these situations include installation of coated abrasive on powertools at low temperatures, installation of adhesive-coated substrates,e.g. tapes, at low temperatures. In these same situations, it is oftennecessary to have high peel strength at high temperatures.

Over the past several years rising energy costs have prompted occupantsof buildings to conserve energy by means of insulation. The installationof shrinkable film or shrinkable/stretchable film over windows by meansof double-stick tape (tape bearing a layer of adhesive on both majorsurfaces thereof) adhered to the interior window frame and to the filmis known to exert a constant force at the film-adhesive interface andprovide a degree of insulation. Normally the film is located between thewindow pane and the interior of the structure. Under normal roomtemperature conditions, the adhesive has physical properties which allowit to maintain the bond. There are many reasons for installinginsulating film on the exterior part of the window. Some users may notwant tape on their interior walls or interior window frames, they maywant ready access to their windows, or they may have ornate window sillsor frames which would hinder installation of the film on the inside. Ifthe film is installed outdoors, the adhesive will be subjected to hightemperatures during summer months and low temperatures during wintermonths. Of particular concern is the fact that, at elevatedtemperatures, the peel strength and shear strength of conventionalpressure sensitive adhesives is greatly reduced. At the same time thefilm is exerting shrink tensions as high as 510 psi causing the bond tofail and the film to pull away from the exterior window frame. Atreduced temperatures conventional pressure-sensitive adhesives havegreatly reduced tack properties, making it difficult to create anadhesive bond with the film or window frame.

Rubber based adhesives, which are normally used for installation ofshrinkable film currently commercially available, exhibit poorweathering characteristics, loss of tack at low temperatures, e.g. 0°C., and loss of shear at high temperatures, e.g. 65° C.

Thus, there is a need for pressure-sensitive adhesives which havebalanced adhesive properties over a wide temperature range, goodadhesion to plastic films which for the most part have low energysurfaces and which can be prepared easily and economically onconventional equipment.

SUMMARY OF THE INVENTION

In one aspect, this invention involves pressure-sensitive adhesiveswhich are useful over a wide temperature range, e.g,. about -45° C. toabout 65° C. The adhesives exhibit excellent adhesion to low energysurfaces, e.g., to the surfaces of films made of polyolefins, such aspolyethylene. In accordance with this invention, there is providednormally tacky and pressure-sensitive adhesive composition comprising ablend of

a. a first component consisting essentially of an emulsifiable, tackypressure-sensitive adhesive, preferably selected from rubber basedadhesives, e.g. thermoplastic elastomers, silicone adhesives, polyvinylacetate modified acrylic adhesives, and polyvinyl acetate adhesives, and

b. a second component which is a copolymer formed from monomersconsisting essentially of

(i) from 95 to 99.8 parts by weight of at least one terminallyunsaturated vinyl monomer, 60 to 100 weight percent of said vinylmonomer being selected from the class of nontertiary alkyl acrylateswherein each alkyl group has at least half of its carbon atoms in asingle chain and the average length of the alkyl chain is at least 4 andnot more than 12, and

(ii) from 0.2 to 5 parts by weight of at least one vinyl-unsaturated,homopolymerizable emulsifier monomer which is a surfactant having both ahydrophobic and a hydrophilic moiety, contains at least 5 but not morethan 40 carbon atoms, and is water-dispersible,

the total parts by weight of (i) plus (ii) being 100, and said secondcomponent preferably contains a small amount of an external emulsifier.

It is preferred that the amount of the second component be sufficient toprovide the pressure-sensitive adhesive composition with higher tack at0° C. than the first component would exhibit if it were alone. Thisadhesive provides excellent tack, peel strength, and shear strength atboth low and high temperatures. Articles bearing this adhesive can beaffixed to various surfaces at low temperatures, e.g. about 0° C. andwill remain adhered thereto at temperatures as high as about 65° C. Byselecting appropriate adhesives for the first component, the adhesive ofthis invention can be tailored to have the characteristics ofrepositionability, removability from both low and high energy surfaces,high peel adhesion with respect to low energy surfaces, and many otherheretofore unavailable properties.

The adhesive can be used as an adhesive mass or it can be applied to oneor both major surfaces of a backing to form a pressure-sensitiveadhesive tape.

In another aspect, this invention involves a kit for providinginsulation comprising the pressure-sensitive adhesive tape of thisinvention and film of the type used to insulate windows, e.g.stretchable film, shrinkable film, or stretchable/shrinkable film.Because the adhesive can be formulated to allow repositioning of thetape and the film, the kit is particularly well-adapted for use byrelatively unskilled installers. Moreover, the temperaturecharacteristics of the adhesive tape render it suitable for outdoor use.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a plan view of a window and window frame wherein a plasticfilm is adhered to the exterior of said window frame by means ofdouble-stick tape bearing the adhesive of this invention.

FIG. 2 is a sectional view of the window and window frame of FIG. 1taken along line 2--2.

DETAILED DESCRIPTION

Adhesives suitable for the first component are emulsifiable, tackypressure-sensitive adhesives. As used herein, the term "tacky" meanshaving sticky nature or immediate adhesion on contact with a substrate.Some adhesives are inherently tacky while others are rendered tacky byaddition of a tackifier. The term "tacky" is intended to refer to bothinherently tacky adhesives and adhesive compositions which include anadded tackifier. The term "emulsifiable" means capable of beingconverted into an intimate mixture of two incompletely miscible liquidsin which one of the liquids in the form of fine droplets is dispersed inthe other.

Although any emulsifiable, tacky pressure-sensitive adhesive can beused, adhesives derived from rubbers, silicones, polyvinyl acetatemodified acrylics, and polyvinyl acetates are preferred for adhesivecompositions that are expected to be removable from various substrates.Examples of rubber based adhesives suitable for the first componentinclude thermoplastic elastomers, such as, for examplestyrene-butadiene-styrene, styrene-isoprene-styrene, andstyrene-ethylene/butylene-styrene. Examples of silicone based adhesivessuitable for the first component include silicone elastomers or gums.The silicone elastomers or gums are typically provided as solventsolutions of elastomer or gum and MQ resin, such as, for example, thatdescribed in U.S. Pat. No. 4,460,371, incorporated herein by reference,especially col. 5, line 47 through col. 7, line 26, thereof. An exampleof a polyvinyl acetate modified acrylic based adhesive suitable for thefirst component includes a composition containing 56% by weight isooctylacrylate, 40% by weight polyvinyl acetate, and 4% by weight acrylic aciddissolved in ethyl acetate. Representative examples of commerciallyavailable adhesives suitable for the first component include thestyrene-isoprene-styrene elastomer "Kraton 1107" and thestyrene-ethylene/butylene-styrene elastomer "Kraton 1657 ", bothavailable from Shell Chemical Company, and silicone elastomers such as"Silgrip PSA 595", "Silgrip PSA 596", and "Silgrip PSA 6574", allavailable from General Electric Co.

The adhesives of the first component can be tackified by a tackifyingagent, by appropriate modification of the structure of the adhesivemolecule, or by a combination of both approaches. Tackifiers suitablefor tackifying the pressure-sensitive adhesive of the first componentinclude low molecular weight hydrocarbon resins, and α- and β-pinenebased resins. Many tackifiers are commercially available, and optimumselection thereof can be accomplished by one of ordinary skill in theadhesive compounding art. Representative examples of commerciallyavailable tackifiers include the resins available under the trademarks"Regalrez 1018" and "Regalrez 1078", both available from HerculesIncorporated, "Exxon ECR 111", "Exxon ECR 327", and "Exxon ECR 328", allavailable from Exxon Corporation, and "Wingtack Plus", available fromFirestone Tire and Rubber Co. The ratio of tackifier to adhesive in thefirst component preferably ranges from about 0.5:1.0 to about 1.5:1.0.

The second component of the adhesive of the present invention ispreferably the copolymer described in Assignee's copending applicationU.S. Ser. No. 666,269, filed Oct. 29, 1984 now U.S. Pat. No. 4,629,663,incorporated herein by reference in total for the description of thatcopolymer. The copolymer is formed from monomers consisting essentiallyof

(a) from 95 to 99.8 parts by weight of at least one terminallyunsaturated vinyl monomer, 60 to 100 weight percent of said vinylmonomer being selected from the class of nontertiary alkyl acrylateswherein each alkyl group has at least half of its carbon atoms in asingle chain and the average length of the alkyl chain is at least 4 andnot more than 12, and

(b) from 0.2 to 5 parts by weight of at least one vinyl-unsaturated,homopolymerizable emulsifier monomer which is a surfactant having both ahydrophobic and a hydrophilic moiety, contains at least 5 but not morethan 40 carbon atoms, and is water-dispersible,

the total parts by weight of (a) plus (b) being 100, and said secondcomponent preferably contains a small amount of an external emulsifier.

The second component can be made with terminally unsaturated vinylmonomers as disclosed in Col. 3, line 28 through col. 4, line 2 ofSilver, U.S. Pat. No. 3,922,464, incorporated herein by reference.Representative examples are listed below in Table A.

TABLE A Acrylate Monomers

isooctyl acrylate

isononyl acrylate

Modifying Comonomers

N-tert-octylacrylamide

N-tert-butylacrylamide

N-tert-amylacrylamide

N-isopropylacrylamide

isobutyl acrylate

ethyl acrylate

N-tert-octylacrylamide has the formula CH₂ ═CHCONHC(CH₃)₂ CH₂ C(CH₃)₃.

The emulsifier monomer preferably comprises a monovalent salt of astyrene sulfonate. A monovalent salt of a styrene sulfonate reliablyproduces substantially coagulum-free latices, both the latices andpolymers produced therefrom tend to have greater hydrolytic stability,and latices of higher solids can be obtained which are easier to coat.By substantially coagulum-free is meant a latex which neither hangs upon a stirrer nor prematurely plugs up a filter. A substantiallycoagulum-free latex can be obtained without external emulsifier,although at least 0.05 weight percent of external emulsifier would bepreferred in commercial production to provide a margin of safety.Preferably the external emulsifier is noncationic and does not exceed1.5 percent by weight of the second component.

Preferably from 0.5 to 2 weight percent of a monovalent salt of styrenesulfonate is used in making the copolymer of the second component inorder to attain desirably high shear values. To employ above about 5weight percent of a monovalent salt may make it difficult to maintaindesirable peel adhesion values.

Latices of the second component can be made (1) by a singlemonomer-charge process, (2) by incremental or continuous monomer feedprocesses, and (3) by seed polymerization. A seed latex may have acomposition different from that of the final latex. For example, theseed latex may omit the emulsifier monomer. Both persulfate andpersulfate-redox initiator systems can be used.

Another class of copolymers that can be used as the second component inthe present invention is that described in U.S. Pat. No. 3,922,464,incorporated herein by reference in total. The copolymer describedtherein is formed of monomers consisting essentially of

a. from 88 to 99 parts by weight of at least one terminally unsaturatedvinyl monomer, 70 to 100 weight percent of said vinyl monomer beingselected from the class of non-tertiary alkyl acrylates wherein eachalkyl group has at least half of its carbon atoms in a single chain andthe average length of the alkyl chain is more than 4 and not more than12,

b. from 0.2 to 5 parts by weight of at least one vinyl-unsaturated,homopolymerizable emulsifier monomer which is a surfactant having both ahydrophobic and a hydrophilic moiety, contains at least 5 but not morethan 40 carbon atoms and is nonionic and/or water-dispersible, and

c. from 0 to 10 parts by weight of at least one zwitterion monomerhaving a free radically polymerizable unsaturated group,

the total parts by weight of (b) plus (c) being at least 1 and not morethan 12, and the total parts by weight of (a) plus (b) plus (c) being100.

Suitable emulsifier monomers are set forth in column 4, line 12 throughline 51 in U.S. Pat. No. 3,922,464. Suitable zwitterion monomers are setforth in column 4, line 63 through column 7, line 5 in U.S. Pat. No.3,922,464. Suitable terminally unsaturated vinyl monomers are set forthin column 3, line 34, through column 4, line 2 in U.S. Pat. No.3,922,464.

This adhesive differs from the preferred adhesive of the secondcomponent in two aspects:

(1) 70 to 100 weight percent, rather than 60 to 100 weight percent, ofthe vinyl terminally unsaturated monomer must be selected from thedesignated class of non-tertiary alkyl acrylates;

(2) at least one zwitterion monomer having a free radicallypolymerizable unsaturated group may be incorporated into the adhesivecomposition.

The preferred adhesive of the second component differs from the adhesiveof U.S. Pat. No. 3,922,464 in that the emulsifier monomer comprises amonovalent salt of a styrene sulfonate. As compared to emulsifiermonomers named in U.S. Pat. No. 3,922,464, a monovalent salt of astyrene sulfonate more reliably produces a substantially coagulum-freelatices, both the latices and polymers produced therefrom tend to havegreater hydrolytic stability, and latices of higher solids can beobtained which are easier to coat.

The adhesives in all but one of the examples in U.S. Pat. No. 3,922,464require zwitterion monomer to provide good adhesion and cohesion.

A preferred method of preparing the adhesive of this invention isdescribed below. A solution containing the emulsifiable, tacky adhesivewhich forms the first component of the adhesive composition of thisinvention is prepared by combining the following ingredients in theamounts indicated:

    ______________________________________                                                           Amount                                                     Ingredient         (parts by weight)                                          ______________________________________                                        Adhesive           100                                                        Solvent            sufficient to make a                                                          solution comprising                                                           from about 5 to about                                                         60% solids                                                 Tackifier (if required)                                                                          about 50 to about 150                                      Antioxidant (if required)                                                                        up to about 1                                              ______________________________________                                    

It is strongly preferred that the solvent used to dissolve the adhesiveof the first component have low polarity and low hydrogen bonding. Aspolarity of the solvent increases, it tends to mix with water utilizedto prepare an aqueous emulsion and emulsion stability may be impaired.The solvent is preferably selected from toluene, xylene, VM+P naphtha,heptane, methylene chloride or mixtures thereof.

The resulting solution is then converted into an emulsion by theaddition of from about 10 to 70 parts by weight water and from about0.25 to about 10 parts by weight surfactant. A portion of the water,preferably no more than about 25 percent by weight, can be replaced byalcohol, e.g., monohydric alcohol having 1 to 6 carbon atoms. It isnecessary to convert the solution containing the adhesive into anemulsion so that it can be readily combined with the second component,which is typically provided in the form of an emulsion. Preferably, thesolution is premixed with non-ionic surfactant, and the water ispremixed with anionic surfactant before the solution is combined withthe water to form the emulsion. For example, for each 100 parts byweight adhesive solution, about 0.55 part by weight non-ionic surfactantis typically added to the adhesive solution, and for each 20 parts byweight water, 0.28 part by weight anionic surfactant is typically addedto the water.

It has been found that a small amount of anionic surfactant can be usedto replace a larger amount non-ionic surfactant, the result being thatthe total amount of surfactant needed is reduced. Up to 50% by weight ofnon-ionic surfactant can be replaced by a lesser percentage by weight ofanionic surfactant. For example, if one part by weight of non-ionicsurfactant were normally required, 0.5 part by weight of non-ionicsurfactant could be replaced by less than 0.5 part by weight of anionicsurfactant. A non-ionic surfactant suitable for the present invention isdesignated by the trademark "Triton X-100", available from Rohm and HaasCo. An anionic surfactant suitable for the present invention isdesignated by the trademark "Triton X-200", available from Rohm and HaasCo. The amount of surfactant must not be so high that it will adverselyaffect the tack, peel strength, and shear strength of the ultimateadhesive. Surfactants to be added to the first component preferably havean HLB value of from about 10 to about 15.

It is preferred that the water used to form the emulsion be deionized,as deionized water provides greater emulsion stability.

It has also been found that when the particulate material contained inthe emulsion is of relatively small size, e.g. having a mean diameter offrom about 1 to about 35 micrometers, the resulting adhesive has bettershear and peel characteristics. Determination of the size of particulatematerial in the emulsion can be accomplished by visual observation withthe aid of a microscope.

The second component of the adhesive, can be prepared according to theprocedure described in assignee's U.S. Ser. No. 666,269, filed Oct. 29,1984, previously incorporated by reference. This second component isthen preferably dissolved in sufficient water, preferably deionizedwater, to form an aqueous emulsion. The aqueous emulsion of the firstcomponent is then combined with the aqueous emulsion of the secondcomponent to form the adhesive of the present invention. The ratio offirst component to second component in pressure-sensitive adhesives ofthis invention preferably ranges from about 5:1 to about 1:5, and morepreferably ranges from 1:1 to 1:3. Ratios outside of these ranges canalso be used to prepare useful pressure-sensitive adhesives; however,operating outside of the preferred range may reduce the breadth of thetemperature range over which the adhesives will be useful.

Adhesive compositions according to the present invention preferablyinclude an anti-oxidant to inhibit oxidation of the tackifying agent andconsequent loss of tackiness as the adhesive composition ages. In thisregard, it has been found important to use an anti-oxidant which isbased on either (1) a hindered phenol or (2) a sulfur-containingorgano-metal salt. Among the hindered phenols are the ortho-substitutedor 2,5-di-substituent group is a branched hydrocarbon radical having3-20 carbon atoms, e.g., tertiary butyl or tertiary amyl. Other hinderedphenols useful in practicing the invention include para-substitutedphenols where the substituent groups is --OR, R being methyl, ethyl,3-substituted propionic ester, etc. Among the sulfur-containingorgano-metal salts are the nickel derivatives of dibutyldithiocarbamate.

Inorganic fillers such as calcium carbonate, clay, talc, silica, andlimited amounts of carbon black can be used with the adhesives of thisinvention, as well as organic fillers such as wood flour or starch.Calcium carbonates, clays and talcs are most commonly used.

Various levels of fillers can be used to significantly reduce costs offormulations containing the adhesives of this invention. Lower levelswill scarcely affect properties, whereas higher levels will appreciablyincrease stiffness, hardness, and resistance to deformation. Very fineparticle size fillers, such as bentonite clay or a fumed silica soldunder the trade designation "Cab--O--Sil" (Cabot Corporation), can beused to increase viscosity of solutions or to impart thixotropicsolution properties.

The adhesives of this invention can be easily colored by compoundingwith dry pigments or color concentrates (usually polystyrene based).Because the base polymers are virtually clear and colorless, lowerlevels of pigments are required than with many other rubbers. Sometypical pigments which may be used are titanium dioxide and carbonblack.

The adhesives of this invention require little or no added stabilizersfor many applications. Thus, in most formulations, ingredients otherthan the adhesive of the first component and copolymer of the secondcomponent will degrade first. Therefore, the kind or type ofstabilization required is highly dependent on the formulation ratherthan on the nature of the adhesive of the first component or copolymerof the second component.

Various stabilizer systems, as well as fungicides and mildewcides, areentirely compatible with the adhesives of this invention.

The resistance to ultraviolet light degradation of the adhesives of thisinvention can be enhanced by incorporating ultraviolet inhibitors intothe adhesive composition of the invention. Typically a 1 phr loading ofthe ultraviolet inhibitor "Cyasorb IV 531" (American Cyanamid Co.), or amixture of equal parts of ultraviolet inhibitors "Tinuvin 327"(Ciba-Geigy Corp.) and "Cyasorb UV 2300" (American Cyanamid Co.) issufficient to provide this enhancement. Enhanced results may be achievedfrom a combination of 0.5 phr or one of the three just mentionedultraviolet inhibitors with one of the following nickel chelates: 0.5phr "Cyasorb UV 1084" (American Cyanamid Co.) or 0.1 phr "NBC" (E.I. DuPont de Nemours). As used herein, phr is based on the weight of thefirst component.

In order to form a pressure-sensitive adhesive tape with the adhesive ofthis invention, the adhesive need merely be applied to a suitablebacking in a conventional manner, e.g. by knife coating or Mayer barcoating, and heating the coated backing to about 85° C. to 95° C. toremove excess moisture. For many purposes, it is preferred that theadhesive be coated on both sides of a tape backing, so that the tape canbe adhered to two substrates. It is also preferred that the backing bemade of transparent, flexible material.

The backing to which the coating of pressure-sensitive adhesive isapplied may be cellophane or cellulose acetate. Other films, forexample, films of ethyl cellulose, plasticized vinyl acetate-vinylchloride copolymers, terephthalic acid-ethylene glycol polyester resins,and the like, are also effective as backings for use in connection withthese adhesives. Backings made of non-woven materials may also be used.Where the adhesive is also transparent, a transparent pressure-sensitiveadhesive tape is produced.

The backing may be given a preliminary adhesive priming coat if desired,although the adhesive herein described is ordinarily found to becomefirmly adherently bonded to most backings even in the absence of suchpriming layer. Colored films may be substituted, and colors or pigments,or contrasting opacifiers, may be incorporated in the adhesive, wherecolored tape products are desired.

Fibrous backings may also be employed, including treated or untreatedpaper, cloth, wadding, and the like. Tape products which are designedprimarily for package sealing will ordinarily comprise cellophane orsome equivalent thin, flexible and strong sheet material. However, ithas been found that such coated sheets or strips have advantages inconnection with adhesive bonding to many surfaces other than kraftpaper, and hence no limitation is to be implied with respect either tothe type of backing employed or to the type of surface to which thecoated product is to be adhered.

The pressure-sensitive adhesive coated tapes of this invention have beenfound to possess an unusually desirable combination of bondingproperties with regard to metal and wood surfaces. It has been found,for example, that such a pressure-sensitive adhesive tape adheresreadily and firmly to clean surfaces of wood, aluminum sheet, and thelike, when pressed thereagainst at low or high temperatures. The tapemay then be removed by cautious stripping, and replaced, as many timesas desired. With some of these adhesive compositions, adhesion to thesurface is found to increase substantially when the tape is allowed toremain adherently attached to such surfaces for even a few hours. Underthese conditions, many types of adhesive-coated backings are found to bepermanently bonded to the surface so that they cannot be effectivelyremoved. The same effect is obtained on other metallic surfaces and onpainted or enameled surfaces.

Adhesive surfaces, and particularly those which tend to form a permanentbond with another surface on prolonged contact therewith, may beprotected and preserved by means of suitable low-adhesion liners orcoverings, of which polylethylene or other high molecular weight waxytype materials are exemplary, either in film form or as a surfacecoating on paper or other supporting web. Other suitable coatingmaterials which serve as effective low-adhesion backsizes or coatingsare described in U.S. Pat. Nos. 2,532,011 and 2,607,711.

When a tape surface bearing the adhesive of this invention is observedby means of a microscope at 3X, it can be seen that the surface ischaracterized by discrete regions of the component that is present inlower concentration dispersed within larger regions of the componentthat is present in higher concentration. In other words, the layer ofadhesive does not exhibit a homogeneous surface.

If the first component of the adhesive were used alone, and ifthermoplastic elastomers or silicones were employed as the adhesive,adhesion between the tape and insulating film would be unsatisfactory athigh temperatures, e.g. at about 65° C. If polyvinyl acetate adhesivewere used instead of thermoplastic elastomers or silicones, the adhesionbetween the tape and the insulating film would be unsatisfactorythroughout the entire temperature range. If the second component of theadhesive were used alone, adhesion between the tape and insulating filmsmade of polyethylene would not be satisfactory throughout the entiretemperature range. The combination of the first component and secondcomponent provides both adhesion stability at high temperatures andinitial adhesion (tack) at low temperatures.

The adhesive tape of this invention exhibits several advantages over theprior art:

(1) It exhibits adhesion over a wide temperature range, namely -45° C.to 65° C. Accordingly, it can be used for adhering films thereto atrelatively low temperatures and the film resists detachment from theadhesive at relatively high temperatures.

(2) It exhibits tack at relatively low temperatures, e.g. 0° C. Thus itcan be adhered to various substrates under conditions which formerlyrendered adhesion difficult, if not impossible.

(3) It allows repositioning of polymeric films applied thereto; itallows repositioning of itself on substrates to which it is applied.

(4) Even though it is capable of forming strongly adhering bonds, it canbe cleanly removed from most substrates after it has been in place forperiods of time of up to a year.

(5) It is capable of being adhered to a variety of substrates, e.g.,painted wood, metal, vinyl.

(6) It is capable of being adhered to a variety of low energysubstrates, e.g., polyolefin film, such as, for example, polyethylene.

(7) It has excellent resistance to degradation from ultravioletradiation.

The following examples, which are illustrative rather than limiting ordelineative of the scope of the invention, serve to describe the noveladhesives, their method of preparation, their properties, and theiruses.

EXAMPLES

In each of the following examples, the same procedure was used toprepare the pressure-sensitive adhesive tapes. All amounts are in partsby weight unless otherwise indicated. This procedure was as follows:

Preparation of First Component The adhesive and the tackifier in theamounts indicated were dissolved in toluene. In Examples 1, 3, and 4,the total amount of "Triton X-100" surfactant was added to theadhesive/tackifier/toluene solution. Then deionized water containing nosurfactant was added to the adhesive/tackifier/toluene solution, and anemulsion was prepared by means of high speed mixing. In Example 2, thetotal amount of "Triton X-100" surfactant and one-half of "Triton X-200"surfactant were added to the adhesive/tackifier/toluene solution. Thendeionized water containing the remaining one-half of "Triton X-200"surfactant was added to the adhesive/tackifier/toluene solution, and anemulsion was prepared by means of high speed mixing. Preparation ofSecond Component

To a vessel fitted with a variable speed agitator, condenser, purgingtube for introducing nitrogen, and a recording controller were added thefollowing materials while purging the flask with nitrogen:

    ______________________________________                                                              Amount                                                  Ingredient            (parts by weight)                                       ______________________________________                                        Deionized water       1477.0                                                  Sodium bicarbonate    2.19                                                    Sodium dodecyl benzene sulfonate                                                                    5.5                                                     Sodium styrene sulfonate                                                                            18.3                                                    Isooctyl acrylate     1591.0                                                  N--tert-octylacrylamide                                                                             219.5                                                   ______________________________________                                    

The solid N-tert-octylacrylamide was dissolved in the isooctyl acrylatebefore adding to the vessel. The nitrogen purge was continued until theend of the run. The vessel and its contents were heated to 50° C., atwhich temperature a first initiator charge of 4.57 parts of a 5% aqueoussolution of potassium persulfate were added.

A change in color of the emulsion indicated the start of polymerization.The temperature was held near 50° C. by cooling and heating during theremaining period of reaction. 9.16 Parts of a 5% solution of potassiumpersulfate were added 6 hours and 45 minutes after the first potassiumpersulfate charge. After 3 hours and 20 minutes, 1.85 parts of a 5%aqueous solution of sodium meta-bisulfite were added. Nine identicaladditional charges of a 5% aqueous solution of sodium meta-bisulfitewere added at intervals of about 45 minutes to complete the reaction,and the final batch was held for one hour after the additions beforecooling.

Preparation of Adhesive Composition

The emulsion containing the first component was then combined with theemulsion containing the second component. In order to form thepressure-sensitive adhesive tapes of this invention, the combinedemulsions were coated on a polyester backing, and the water and tolueneremoved by heating at 85° C. to 95° C. for 10 minutes.

The ingredients and amounts thereof used to prepare examples of adhesivecompositions within the scope of this invention and comparative examplesare set forth in Table I.

                                      TABLE I.sup.1                               __________________________________________________________________________              A    B    C    D                                                    Ingredient                                                                              (Comp.)                                                                            (Comp.)                                                                            (Comp.)                                                                            (Comp.)                                                                            1   2   3  4                                    __________________________________________________________________________    First Component                                                               Rubber based                                                                  adhesive                                                                      Kraton 1657                                                                             18.80                                                                              17.60                                                                              18.90     9.70                                                                              5.00                                                                              10.20                                                                            9.00                                 Tackifier                                                                     Exxon ECR 111  26.40                  15.40                                   Exxon ECR 327        9.60                4.60                                 Exxon ECR 328       18.90                9.00                                 Regalrez 1078                                                                           18.80               9.70                                                                              5.00                                        Regalrez 1018                                                                            1.90               1.00                                                                              1.50                                        Surfactant                                                                    Triton X-100                  0.50                                                                              0.16                                                                               1.10                                                                            0.50                                 Triton X-200                      0.30                                        Solvent                                                                       Toluene   59.70                                                                              55.40                                                                              52.00     30.72                                                                             17.80                                                                             43.60                                                                            25.00                                Antioxidant                                                                   Irganox 1076                                                                             0.40                                                                               0.30                                                                               0.30     0.14                                                                              0.12                                                                               0.20                                                                            0.15                                 Cyanox LTPD                                                                              0.40                                                                               0.30                                                                               0.30     0.14                                                                              0.12                                                                               0.20                                                                            0.15                                 Water                         10.30                                                                             5.90                                                                              17.30                                                                            9.60                                 Second Component.sup.2   100  37.80                                                                             64.10                                                                             12.00                                                                            42.00                                __________________________________________________________________________     .sup.1 All amounts are in parts by weight.                                    .sup.2 The second component is a terpolymer formed from isooctyl acrylate     octylacrylamide, and sodium styrene sulfonate.                           

TEST PROCEDURES

A number of industry-recognized tests are commonly employed tocharacterize the performance of normally tacky and pressure-sensitiveadhesive tapes. A brief summary of the tests employed to evaluateadhesives herein is described below:

Qualitative Tack 32° F. (0° C.). The qualitative "touch test" ratingsare subjective tack ratings made by a 4-6 member tack panel. A 1.27 cmby 15.24 cm polyethylene film is used to test the tack of the adhesiveat 0° C. The film is applied to the adhesive with a consistent pressure.Then the film is pulled off the adhesive at a 180° angle at a constantrate. The adhesive is rated on a 1-4 scale, 1 being no tack, 2 being lowtack, 3 being good tack, and 4 being excellent tack.

Peel Adhesion. The test is a modification of PSTC-1, described in "TestMethods of Pressure-Sensitive Tapes", 7th Edition, Pressure-SensitiveTape Council, Glenview, Ill., 1976. A solution of the adhesive to betested is coated on a release liner in a quantity such that, uponevaporation of the solvent, the weight of adhesive remaining isapproximately 0.91 grams per 10.56 cm×15.24 cm. Strips 15 cm long and2.54 cm wide are cut from the tape and placed in contact with thesubstrate to which adhesion is to be determined. Substrates to be usedare glass, polyethylene film, and latex painted wood. The glass is to becleaned after each adhesive is tested using one wash of diacetonealcohol (technical grade) and three washes of heptane (analyticalgrade). The painted wood and the film are to be used only once. Theliner is removed and using two passes of a 1.82 kg roller, the adhesivesurface of the tape is forced into contact with the substrate. One endof the tape is doubled back on itself at 180° , the exposed portion ofthe substrate being clamped in the upper jaws of a tensile testingmachine while the doubled-back end of the tape is clamped in the lowerjaws. The jaws are then separated at a rate of 35.7 cm/minute, the forceto effect separation being reported in g/cm width.

Shear Adhesion (Holding Power). As used herein, this test is amodification of PSTC-7, described in the same publication referred to inthe peel adhesion tests. A 1.27 cm×15.25 cm specimen of the adhesivedescribed in the preceding two tests is mounted on a 7.5 cm×7.5 cmbrushed stainless steel panel. The panel is then positioned with itslong dimension at 2° from vertical so that the back of the panel formsan angle of 178° with the extended piece of tape, the 1.27 cm dimensionof the adhesive extending in the vertical direction. The assembly isthen placed in a 23° C. oven (50% relative humidity) and a 500 g weightattached to the free end of the tape. The cohesive strength of theadhesive is less than its adhesion to the brushed steel panel and thetime required for the adhesive to fail cohesively, as evidenced by thetape falling free, is recorded as the shear in minutes.

Ultraviolet Stability (QUV). This procedure tests the stability of boththe adhesive and film adhered tape coated with the adhesive underaccelerated weathering conditions.

The double-coated adhesive tape is adhered onto a panel and one-half ofthe tape is covered with a piece of polyethylene film. The test sampleis visually observed every twenty-four hours for cracks, yellowing, ordegradation of the adhesive. The time to failure is reported in hours.

Stretched Film Test 140° F. (60° C.). The exposed side of the test tapeis placed adhesive side down onto the outer edge of the latex paintedwindow frame. The adhesive is pressed in place with even pressure. Theliner is then removed and the film applied by stretching the film tautlyacross the window. The window with the film attached is placed into anoven at 49° C. for 24 hours. The test article is observed for failure toeither the film or the wood. Observations are made at 2 hour intervals.If the adhesive does not fail at 49° C., the temperature is raised to54° C. and observed for an additional 24 hours. If no failure ispresent, the temperature is increased to 60° C. The test article is thenobserved for failure or until 72 hours have passed. The time to failureis reported in hours and the type of failure observed is noted.

The results of the above-mentioned tests are set forth in Table II.

                                      TABLE II                                    __________________________________________________________________________              Adhesion to various                                                                            Shear,                                                                              Stretched film                               Tack      substrates, g/cm.sup.1                                                                  QUV, hours                                                                           minutes to                                                                          test (60° C.),                        Example                                                                             (0° C.)                                                                    G  PW  PE to failure.sup.2                                                                     failure                                                                             hours to failure.sup.3                       __________________________________________________________________________    A (Comp)                                                                            1   580                                                                              312 357                                                                              100     10,000+                                                                             1                                           B (Comp)                                                                            1   982                                                                              469 670                                                                              165     10,000+                                                                             1                                           C (Comp)                                                                            1   692                                                                              179 357                                                                              72     8,178  1                                           D (Comp)                                                                            4   379                                                                              268 156                                                                               200+   10,000+                                                                            12                                           1     4   603                                                                              380 335                                                                               200+    198  48+                                         2     4   513                                                                              402 223                                                                               200+   4,200+                                                                              48+                                         3     4   558                                                                              290 491                                                                              158      577  24+                                         4     3   513                                                                              346 446                                                                              178      290 36                                           __________________________________________________________________________     .sup.1 G represents glass; PW represents printed wood; PE represents          polyethylene                                                                  .sup.2 QUV is a measure of accelerated weathering. It was measured on an      accelerated weathering tester manufactured by Q Panel Co. under the           following conditions: exposure to ultraviolet light for 4 hours followed      by exposure to the following humidity conditions for 4 hours (40°      C., 100% relative humidity)                                                   .sup.3 Polyethylene film (RD 102, manufactured by W. R. Grace & Co.) was      applied to a strip of tape. The composite was subjected to 140 F until th     bond was split. The time of failure was recorded.                        

Comparative examples A, B, C and D are formulations of prior artadhesives that can be combined to make up the adhesive composition ofthe present invention. Formulations A, B, and C are compositionscomprising rubber based adhesives and different tackifiers. Each ofthese adhesive formulations is characterized by having good peeladhesion to various substrates at room temperature (25° C.) and havingshear of 8000 minutes or greater. All of the rubber based adhesives arecharacterized by having low tack at 0° C. and having poor adhesion at65° C. Each of these adhesives failed the stretched film test after only1 hour at 65° C.

The terpolymer used in formulation D has excellent low temperature tack.At 65° C. polymeric film loses adhesion to the adhesive of formulation Dafter only 12 hours. The adhesion of formulation D to various surfacesis much lower than that of formulations A, B, or C but is adequate forreasonable performance.

Examples 1, 2, 3, and 4 are adhesive compositions of this invention.Example 2 is the preferred composition. Each of these adhesivecompositions perform adequately through a temperature range of -40° C.to 68° C. The shear in minutes is not as high as that of thecompositions of comparative examples A, B, C, or D but is adequate tomeet performance requirements. The tack at 0° C. is excellent. Thisindicates that polymeric film can be applied to a tape bearing theadhesive composition of this invention at a low temperature. Tapes usingthe adhesive compositions of Example 1 and 2 did not fail the stretchedfilm test even after 48 hours. Adhesive compositions of Examples 3 and 4failed the stretched film test before 48 hours were reached.

EXAMPLE 5

FIGS. 1 and 2 illustrate one of the many uses of the present invention,namely, to affix a sheet of polymeric film to a window frame to providea means of insulation. The tape of this invention is preferably providedin a roll. Each major surface of the tape bore a layer of the adhesivedescribed in Example 2, supra. Thus, the tape is designated adouble-stick tape. It is preferable that the surface of the tape that isto contact the window frame exhibit a peel adhesion value sufficientlyhigh that the tape will not detach from the frame when the insulatingfilm is being repositioned. However, it is preferable that the surfaceof the tape that is to contact the insulating film exhibit a peeladhesion value sufficiently low that the insulating film can berepositioned before final mounting. If the same adhesive composition isused on both major surfaces of the tape, it is preferred that thequantity of adhesive on the surface to contact the polymeric film beless than the quantity of adhesive on the surface to contact the windowframe so that the polymeric film can be easily repositioned withoutdetaching the tape from the window frame. In this particular case, thesurface of the tape intended to contact the window frame had an adhesivecoating density of 0.91 grains/ 10.16 cm×15.24 cm, and the surface ofthe tape intended to contact the insulating film had an adhesive coatingdensity of 0.46 grains/10.16 cm×15.24 cm. Differential adhesion valuescan be attained by other means, e.g. by using a different adhesivecomposition on each surface of the tape. The adhesive on the surfacethat is to contact the film is preferably covered with a protectiverelease liner for the reasons previously stated. Preferred materials forthe polymeric film are polyester, e.g. polyethylene terephthalate,polyolefin, e.g., polyethylene, polypropylene, and cellophane. Thethickness of the film preferably ranges from 0.015 to 0.070 mm. Thepreferred film is a 0.02 mm radiation-crosslinked polyethylene. The filmcan be transparent or tinted to reduce sunlight and glare. It is alsopreferred that the film be shrinkable, by heat, or stretchable, bytension, so that wrinkles in the film can be removed after installation.If the film is shrinkable, it is preferred that the shrinkage be between1 and 10% in both directions at 70° C. as measured in accordance withASTM-D-2732 (1976). If the film is stretchable, it is preferred that thefilm have a bulk modulus of between 8000 and 120,000 psi and anelongation of 75 to 600% as measured in accordance with ASTM-D-882(1981). Furthermore, it is preferred that the film be capable ofwithstanding temperatures of from about -50° C. to about 65° C. and havea transparency greater than 85% as measured in accordance withASTM-D-1003 (1977). A representative example of a film suitable forwindow insulation purposes is available from W. R. Grace & Co. and hasthe trade designation "RD-102". This film is a heat shrinkable and/orstretchable radiation crosslinked bi-axially oriented blown polyethylenefilm.

The tape 10 is unwound from the roll and is affixed to window frame 12by means of adhesive surface 14 thereof. The release liner (not shown)is removed from adhesive surface 16 of tape 10, thus exposing theadhesive for attachment to polymeric film 18. A thin, preferablytransparent, polymeric film 18 can then be affixed to window frame 12with the available surface 16 of double-stick tape 10 so that there isgap between film 18 and window pane 20.

Within the first few minutes after application, the film can be removedand repositioned without adhesive transfer or film distortion. Within anhour, however, adhesion has increased significantly. The film can betrimmed, as with scissors or razor blade, so that excess film materialwill not extend beyond the edge of the double-stick tape.

For standard sized windows, prefabricated film with double-stick tapeadhered thereto can be used. The tape would have a protective releaseliner on the surface of the tape to prevent the tape from adhering toitself prior to use. The protective release liner would be removedbefore the polymeric film is installed on the window frame. Wrinkles inthe film can be removed by subjecting the film to tension, if it isstretchable, or to heat, as with a heat-gun or hair dryer, if it isheat-shrinkable. While the initial adhesion is relatively low, it buildsto a strong bond within a brief time.

Various modifications and alterations of this invention will becomeapparent to those skilled in the art without departing from the scopeand spirit of this invention, and it should be understood that thisinvention is not to be unduly limited to the illustrative embodimentsset forth herein.

What is claimed is:
 1. Tape having a backing bearing on at least onemajor surface thereof an adhesive composition consisting essentiallyof(a) a first component consisting essentially of a tacky adhesive thatis capable of being emulsified in water, and (b) a second componentconsisting essentially of(i) from 95 to 99.8 parts by weight of at leastone terminally unsaturated vinyl monomer, 60 to 100 weight percent ofsaid vinyl monomer being selected from the class of nontertiary alkylacrylates wherein each alkyl group has at least half of its carbon atomsin a single chain and the average length of the alkyl chain is at least4 and not more than 12, and (ii) from 0.2 to 5 parts by weight of atleast one vinyl-unsaturated, homopolymerizable emulsifier monomer whichis a surfactant having both a hydrophobic and a hydrophilic moiety,contains at least 5 but not more than 40 carbon atoms, and iswater-dispersible, the total parts by weight of (i) plus (ii) being 100,the surface of said tape bearing said adhesive composition havingdiscrete regions of said first or said second component that is presentin lower concentration dispersed within regions of said first or saidsecond component that is present in higher concentration.
 2. The tape ofclaim 1 wherein said backing comprises a polymeric material.
 3. Kit forinsulation comprising the tape of claim 1 and polymeric film.
 4. The kitof claim 3 wherein said polymeric film is shrinkable.
 5. The kit ofclaim 3 wherein said polymeric film is stretchable.
 6. The kit of claim3 wherein said polymeric film is shrinkable and stretchable.
 7. Tapehaving a backing bearing on both major surfaces thereof an adhesivecomposition consisting essentially of(a) a first component consistingessentially of a tacky adhesive capable of being emulsified in water,and (b) a second component consisting essentially of(i) from 95 to 99.8parts by weight of at least one terminally unsaturated vinyl monomer, 60to 100 weight percent of said vinyl monomer being selected from theclass of nontertiary alkyl acrylates wherein each alkyl group has atleast half of its carbon atoms in a single chain and the average lengthof the alkyl chain is at least 4 and not more than 12, and of at least(ii) from 0.2 to 5 parts by weight one vinyl-unsaturated,homopolymerizable emulsifier monomer which is a surfactant having both ahydrophobic and a hydrophilic moiety, contains at least 5 but not morethan 40 carbon atoms, and is water-dispersible, the total parts byweight of (i) plus (ii) being 100, the surface of said tape bearing saidadhesive composition having discrete regions of said first or saidsecond component that is present in lower concentration dispersed withinregions of said first or said second component that is present in higherconcentration.
 8. Kit for insulation comprising a tape having a backingbearing a pressure-sensitive adhesive composition on both major surfacesthereof and stretchable polymeric film wherein said adhesive compositionconsists essentially of(a) a first component consisting essentially of atacky adhesive capable of being emulsified in water, and (b) a secondcomponent consisting essentially of(i) from 95 to 99.8 parts by weightof at least one terminally unsaturated vinyl monomer, 60 to 100 weightpercent of said vinyl monomer being selected from the class ofnontertiary alkyl acrylates wherein each alkyl group has at least halfof its carbon atoms in a single chain and the average length of thealkyl chain is at least 4 and not more than 12, and (ii) from 0.2 to 5parts by weight of at least one vinyl-unsaturated, homopolymerizableemulsifier monomer which is a surfactant having both a hydrophobic and ahydrophilic moiety, contains at least 5 but not more than 40 carbonatoms, and is water-dispersible, the total parts by weight of (i) plus(ii) being 100, the surface of said tape bearing said adhesivecomposition having discrete regions of said first or said secondcomponent that is present in lower concentration dispersed withinregions of said first or said second component that is present in higherconcentration.
 9. Tape having a backing bearing on both major surfacesthereof an adhesive composition consisting essentially of(a) a firstcomponent consisting essentially of a tacky adhesive capable of beingemulsified in water, and (b) a second component consisting essentiallyof copolymer of monomers consisting essentially ofa. from 88 to 99 partsby weight of at least one terminally unsaturated vinyl monomer, 70 to100 weight percent of said vinyl monomer being selected from the classof non-tertiary alkyl acrylates wherein each alkyl group has at leasthalf of its carbon atoms in a single chain and the average length of thealkyl chain is more than 4 and not more than 12, b. from 0.2 to 5 partsby weight of at least one vinyl-unsaturated, homopolymerizableemulsifier monomer which is a surfactant having both a hydrophobic and ahydrophilic moiety, contains at least 5 but not more than 40 carbonatoms and is nonionic and/or water-dispersible, and c. from 0 to 10parts by weight of at least one zwitterion monomer having a freeradically polymerizable unsaturated group, the total parts by weight of(b) plus (c) being at least 1 and not more than 12, and the total partsby weight of (a) plus (b) plus (c) being 100, the surface of said tapebearing said adhesive composition having discrete regions of said firstor said second component that is present in lower concentrationdispersed within regions of said first or said second component that ispresent in higher concentration.
 10. Tape having a backing bearing on atleast one major surface thereof an adhesive composition consistingessentially of(a) a first component consisting essentially of a tackyadhesive capable of being emulsified in water, and (b) a secondcomponent consisting essentially of copolymer of monomers consistingessentially ofa. from 88 to 99 parts by weight of at least oneterminally unsaturated vinyl monomer, 70 to 100 weight percent of saidvinyl monomer being selected from the class of non-tertiary alkylacrylates wherein each alkyl group has at least half of its carbon atomsin a single chain and the average length of the alkyl chain is more than4 and not more than 12, b. from0.2 to 5 parts by weight of at least onevinyl-unsaturated, homopolymerizable emulsifier monomer which is asurfactant having both a hydrophobic and a hydrophilic moiety, containsat least 5 but not more than 40 carbon atoms and is nonionic and/orwater-dispersible, and c. from 0 to 10 parts by weight of at least onezwitterion monomer having a free radically polymerizable unsaturatedgroup, the total parts by weight of (b) plus (c) being at least 1 andnot more than 12, and the total parts by weight of (a) plus (b) plus (c)being 100, the surface of said tape bearing said adhesive compositionhaving discrete regions of said first or said second component that ispresent in lower concentration dispersed within regions of said first orsaid second component that is present in higher concentration.
 11. Kitfor insulation comprising the tape of claim 10 and polymeric film.